Method and system for identifying damage to a wire

ABSTRACT

Methods, systems, and articles of manufacture consistent with the present invention determine the type of damage to a wire, the amount of damage, and the location of the damage based on the wire&#39;s broadband impedance measured from a single measurement point. The type of damage is determined by comparing the wire&#39;s calculated dielectric function, resistance and inductance to known values that correspond to types of wire damage. The amount of damage is determined by comparing the wire&#39;s low-frequency impedance phase to known low-frequency impedance phase information that corresponds to a known amount of wire damage. The location of damage is determined by comparing the wire&#39;s high-frequency impedance phase to known high-frequency impedance phase information that corresponds to a known location of wire damage.

GOVERNMENT CONTRACT

This invention was made with Government support under Contract No.DTFA-03-C-00014 awarded by the FAA. The Government has certain rights inthis invention.

BACKGROUND OF THE INVENTION

The present invention generally relates to the field of electrical wiretesting and, more particularly, to methods and systems for determiningthe type of damage, the amount of damage, and the location of damage toa wire using broadband impedance.

Damaged wiring can lead to detrimental conditions, such as shortcircuits. When the damaged wiring is located in, for example, commercialor military aircraft, space vehicles, or nuclear power plants, thedamaged wiring can lead to serious problems.

Conventional approaches for determining whether a wire is damagedinclude hi-pot and wire insulation tests. Although these conventionalmethods are effective to detect damage in a wire, such as short circuitsusing the hi-pot test or damaged insulation using the wire insulationtest, the conventional tests can break or damage the wire. For example,during a hi-pot test, a high voltage of 500V is typically applied to thewire. Such voltage can damage a delicate wire or thin conductor.Further, conventional approaches determine whether a wire is damaged,but fail to provide the type of damage, the location of the damage, orthe amount of damage.

SUMMARY OF THE INVENTION

Methods, systems, and articles of manufacture consistent with thepresent invention determine the type of damage, the amount of damage,and/or the location of damage to a wire using broadband impedancemeasured from a single measurement point on the wire.

In accordance with methods consistent with the present invention, amethod in a data processing system having a program for identifyingdamage to a wire is provided. The method comprises the steps ofobtaining a broadband impedance information for the wire from a singlemeasurement point, and determining a type of damage to the wire based onthe broadband impedance information.

In accordance with articles of manufacture consistent with the presentinvention, a computer-readable medium containing instructions that causea data processing system having a program to perform a method foridentifying damage to a wire is provided. The method comprises the stepsof obtaining a broadband impedance information for the wire from asingle measurement point, and determining a type of damage to the wirebased on the broadband impedance information.

In accordance with systems consistent with the present invention, a dataprocessing system for identifying damage to a wire is provided. The dataprocessing system comprises: a memory having a program that obtains abroadband impedance information for the wire from a single measurementpoint, and determines a type of damage to the wire based on thebroadband impedance information; and a processing unit that runs theprogram.

In accordance with systems consistent with the present invention, a wireanalyzer for identifying damage to a wire is provided. The wire analyzercomprises means for obtaining a broadband impedance information for thewire from a single measurement point, and means for determining a typeof damage to the wire based on the broadband impedance information.

Other features of the invention will become apparent to one with skillin the art upon examination of the following figures and detaileddescription. It is intended that all such additional systems, methods,features, and advantages be included within this description, be withinthe scope of the invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in an constitute apart of this specification, illustrate an implementation of theinvention and, together with the description, serve to explain theadvantages and principles of the invention. In the drawings,

FIG. 1 is a schematic diagram of a system for analyzing a wire fordamage consistent with the present invention;

FIG. 2 is a block diagram of a data analysis system consistent with thepresent invention;

FIG. 3 is a detail of the wire in FIG. 1;

FIG. 4 is a flow diagram of the exemplary steps for determining a typeof wire damage, the amount of damage, and the location of the damageconsistent with the present invention;

FIG. 5 is a measured frequency-dependent magnitude spectrum of the wireof FIG. 1 for a case in which the wire is in an open-circuitconfiguration;

FIG. 6 is a measured frequency-dependent phase spectrum of the wire ofFIG. 1 for a case in which the wire is in an open-circuit configuration;

FIG. 7 is a measured frequency-dependent magnitude spectrum of the wireof FIG. 1 for a case in which the wire is in a closed-circuitconfiguration;

FIG. 8 is a measured frequency-dependent phase spectrum of the wire ofFIG. 1 for a case in which the wire is in a closed-circuitconfiguration;

FIG. 9 is a flow diagram of the exemplary steps for determining the typeof wire damage consistent with the present invention;

FIG. 10 is a calculated frequency-dependent real dielectric functionspectrum; and

FIG. 11 is a calculated frequency-dependent imaginary dielectricfunction spectrum.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to an implementation in accordancewith methods, systems, and articles of manufacture consistent with thepresent invention as illustrated in the accompanying drawings.

Methods, systems, and articles of manufacture consistent with thepresent invention determine the type of damage, the amount of damage,and/or the location of damage to a wire using broadband impedancemeasured from a single measurement point on the wire.

FIG. 1 depicts a block diagram of a system 100 for detecting andlocating wire damage in a wire consistent with the present invention. Asillustrated, the system 100 generally comprises a wire 102, which may bedamaged, for example, by a short-circuit or degraded insulation. A dataanalysis system 104 is connected to a measurement point 106 of wire 102via a cable 108. Cable 108 electrically connects to wire 102 via one ormore connectors 110, such as a banana clip or other type of connector.Data analysis system 104 measures the broadband impedance of wire 102,determines whether there is damage along the wire, determines the amountof damage, and locates the damage based on the measured broadbandimpedance. Further, data analysis system 104 determines the location ofthe damage at any point along the wire using the measured broadbandimpedance obtained from the single measurement point 106.

FIG. 2 depicts data analysis system 104 in more detail. Data analysissystem 104 comprises an impedance measurement device 202 and a dataprocessing system 204. Impedance measurement device 202 measures themagnitude and phase of the broadband impedance of wire 102, and can be asuitable off-the-shelf impedance measurement device. For example, theimpedance measurement device can be, but is not limited to, the 4294APrecision Impedance Analyzer manufactured by Agilent Technologies, Inc.of Palo Alto, Calif., U.S.A. As impedance measurement devices are knownto those skilled in the art, the impedance measurement device will notbe described in further detail.

During operation, the impedance measurement device outputs a low-voltageoutput signal, which is transmitted through wire 102 via cable 108. Thefrequency of the output signal is adjusted so impedance measurementdevice 202 measures the frequency-dependant impedance of wire 102 acrossa range of frequencies, such as from about 0 Hz to about 100 MHz. Themeasured impedance information is converted to a digital signal by ananalog-to-digital converter 206 and output from the impedancemeasurement device. Once the signal is in a digital form, it can beprocessed by data processing system 204. Collected impedance informationmay be archived in a memory 208 or a secondary storage 210 of dataprocessing system 204.

One having skill in the art will appreciate that the data acquisitionand data collection functionality of data analysis system 102 can beincluded in a device separate from data processing system 204. Theseparate device would comprise an impedance measurement system having ananalog-to-digital converter, a processing unit, and a memory. Thecollected data would be stored on the separate device during dataacquisition and transferred to the data processing system 204 forprocessing.

Data processing system 204 comprises a central processing unit (CPU) orprocessor 212, a display device 214, an input/output (I/O) unit 216,secondary storage device 210, and memory 208. The data processing systemmay further comprise standard input devices such as a keyboard, a mouseor a speech processor (each not illustrated).

Memory 208 comprises a program 220 for identifying the type, amount, andlocation of damage to a wire, such as wire 102. In an illustrativeexample, program 220 is implemented using MATLAB® software, however, theprogram can be implemented using another application program or anotherprogramming language. As will be described in more detail below, theprogram determines the type of damage to a wire by analyzing the wire'sdielectric function, resistance and inductance, analyzes thelow-frequency portion of the phase of the wire's broadband impedanceinformation to determine the amount of the wire damage, and analyzes thehigh-frequency portion of the phase of the wire's broadband impedanceinformation to locate the damage. MATLAB is a United States registeredtrademark of The MathWorks, Inc. of Natick, Mass.

One having skill in the art will appreciate that the program can residein memory on a system other than data processing system 204. Program 220may comprise or may be included in one or more code sections containinginstructions for performing their respective operations. Althoughprogram 220 is described as being implemented as software, the programmay be implemented as a combination of hardware and software or hardwarealone. Also, one having skill in the art will appreciate that program220 may comprise or may be included in a data processing device, whichmay be a client or a server, communicating with data processing system204. Further, data analysis system 104 can itself be an impedancemeasurement device.

Although aspects of methods, systems, and articles of manufactureconsistent with the present invention are depicted as being stored inmemory, one having skill in the art will appreciate that these aspectsmay be stored on or read from other computer-readable media, such assecondary storage devices, like hard disks, floppy disks, and CD-ROM; acarrier wave received from a network such as the Internet; or otherforms of ROM or RAM either currently known or later developed. Further,although specific components of data processing system 204 have beendescribed, one having skill in the art will appreciate that a dataprocessing system suitable for use with methods, systems, and articlesof manufacture consistent with the present invention may containadditional or different components.

Data processing system 204 can itself also be implemented as aclient-server data processing system. In that case, program 220 can bestored on the data processing system as a client, and some or all of thesteps of the processing described below can be carried out on a remoteserver, which is accessed by the client over a network. The remoteserver can comprise components similar to those described above withrespect to the data processing system, such as a CPU, an I/O, a memory,a secondary storage, and a display device.

FIG. 3 depicts the illustrative wire 102 in more detail. As shown, theillustrative wire comprises two conductors 302 and 304, which areillustratively arranged in a twisted-pair configuration. Alternatively,conductors 302 and 304 can be arranged in a different configuration,such as a coaxial or parallel-spaced conductor configuration. Conductors302 and 304 are preferably insulated. The wire has a length (LT), whichis 10 meters in the illustrative example. Wire damage 306 is presentalong the wire from location L₁ to location L₂ and represents, forexample, a short circuit, damaged insulation, or another type of defect.In the illustrative example, the wire damage is damaged insulation inconductor 304 from L₁=5 meters to L₂=6 meters. The damage representsdamage, for example, from humidity or exposure to hydraulic fluid.

Impedance measurement device 202 transmits the low-voltage signal towire 102 via conductors 108 a and 108 b of cable 108. As shown,conductors 108 a and 108 b of cable 108 connect to the conductors ofwire 102 via respective connectors 110 a and 110 b. The low-voltagesignal from the impedance measurement device has a potential of, forexample, a few volts. Thus, there is a lower risk of damaging the wirewith low-voltage signal consistent with the present invention than withconventional test signals that typically have a potential of around 500volts.

FIG. 4 depicts a flow diagram illustrating the exemplary steps performedby program 220 for detecting and identifying the type, amount, andlocation of damage to a wire, such as wire damage 306, on a wire. Aswill be described in more detail below, the program determines the typeof damage to a wire by analyzing the wire's dielectric function,resistance and inductance, analyzes the low-frequency portion of thephase of the wire's measured broadband impedance information todetermine the amount of wire damage, and analyzes the high-frequencyportion of the phase of the wire's measured broadband impedanceinformation to locate the damage. First, the program receives themeasured impedance information for the wire (step 402). The measuredimpedance information can be received, for example, as a data file inthe memory or in the secondary storage. Alternatively, the program canmeasure the measured impedance over a predetermined range of frequenciesand store the frequency-dependent impedance magnitude and phase spectra,for example, in the memory or the secondary storage. In the illustrativeexample, the impedance measurement device measures thefrequency-dependent impedance magnitude and phase spectra and transfersthe information to the data processing system, where the information issaved in a measured-data data file 222 in the secondary storage. Thebroadband impedance data is measured for cases in which the wire is inan open-circuit configuration and a closed-circuit configuration at theend of the wire opposite the measurement point.

The data for the measured impedance magnitude spectrum for theillustrative example, wherein the wire is in an open-circuitconfiguration, is shown in FIG. 5. The phase spectrum for the measuredimpedance data, wherein the wire is in an open-circuit configuration, isdepicted in FIG. 6.

Further, the data for the measured impedance magnitude spectrum for theillustrative example, wherein the wire is in a short-circuitconfiguration, is shown in FIG. 7. The phase spectrum for the measuredimpedance data, wherein the wire is in a short-circuit configuration, isdepicted in FIG. 8.

Then, the program determines whether the wire is damaged by a known typeof damage (step 404). To determine whether the wire is damaged, theprogram calculates the wires frequency-dependent dielectric function(ε(ω)), resistance (R(ω)), and inductance (L(ω)) based on the measuredbroadband impedance of the wire and compares these calculated values toknown values corresponding to various types of damage. Through extensiveexperimentation, the inventors have discovered the frequency-dependentdielectric function, resistance, and inductance contribute to theelectrical properties of the wire and correspond to the state of theinsulation and conductor. For example, the skin effect, which resultsfrom an oxide layer or other type of layer contacting the surface of theconductor, manifests itself in the conductor's resistance. Also, whenthe wire's insulation is affected by various environmental stresses, thewire's dielectric function exhibits two microscopic processes: arelatively slow ionic process that is nearly Debye and a relatively fastelectronic process that is nearly independent of frequency.

FIG. 9 depicts a flow diagram of the process performed in step 404 inmore detail. As shown in FIG. 9, to determine the type of damage, theprogram extracts the real (ε₁(ω)) and imaginary (ε₂(ω)) components ofthe wire's dielectric function (ε(ω)) from the measured impedance data(step 902). A cable, such as the insulated twisted-pair wire of theillustrative example, has a frequency-dependent resistance (R(ω)) permeter, conductance (C(ω)) per meter, inductance (L(ω)) per meter, andconductance (G(ω)) per meter. The capacitance and conductance arerelated to the dielectric function ε(ω) of the cable as shown below inEquation (1).G(ω)+iωC(ω)=Λωε(ω)  Equation (1)In Equation (1), “Λ” is a structure factor that depends on theconfiguration of the insulated wire (e.g., twisted pair) and isindependent of frequency. For the insulated wire of the illustrativeexample, the structure factor Λ can be computed as shown below inEquation (2). $\begin{matrix}{\Lambda = \frac{\pi}{\cosh^{- 1}\left( \frac{s}{d} \right)}} & {{Equation}\quad(2)}\end{matrix}$In Equation (2), “d” represents the diameter of each wire of the twistedpair of the insulated wire and “s” represents a center-to-centerdistance between the conductors of the wires of the insulated wire.

When the impedance measurement device affects a voltage between thewires of the twisted-pair insulated wire, the voltage and current can becomputed by Equations (3) and (4). $\begin{matrix}{{\frac{\partial}{\partial x}{V\left( {x,t} \right)}} = {{{- {I\left( {x,t} \right)}}\quad R} - {\frac{\partial}{\partial t}{{LI}\left( {x,t} \right)}}}} & {{Equation}\quad(3)} \\{{\frac{\partial}{\partial x}{I\left( {x,t} \right)}} = {{- {{GV}\left( {x,t} \right)}} - {\frac{\partial}{\partial t}{{CV}\left( {x,t} \right)}}}} & {{Equation}\quad(4)}\end{matrix}$

The voltage of Equation (3) and the current of Equation (4) define a setof normal node waves A_(±)(x,t) propagating through the insulated wire.A_(±)(x,t) is further shown below in Equation (5).A _(±)(x,t)=exp[±γ(ω)x−iωt]  Equation (5)In Equation (5), “γ” is a propagation function, which can be defined byEquation (6). $\begin{matrix}\begin{matrix}{{\gamma(\omega)} = \sqrt{\left( {{R(\omega)} + {{\mathbb{i}}\quad\omega\quad{L(\omega)}}} \right)\left( {{G(\omega)} + {{\mathbb{i}}\quad\omega\quad{C(\omega)}}} \right)}} \\{= \left( {{\alpha(\omega)} + {{\mathbb{i}}\quad{\beta(\omega)}}} \right)}\end{matrix} & {{Equation}\quad(6)}\end{matrix}$In Equation (6), α(ω) is the dissipation coefficient per meter of theinsulated wire. 2π/β(ω) represents the wavelength of the normal modewave A_(±)(x,t) propagating through the insulated wire. v(ω)=ω/β(ω)represents the speed (v(ω)) at which the signals can propagate on theinsulated wire. The propagation function can be rewritten as shown belowin Equation (7).γ(ω)=√{square root over ((R(ω)+iωL(ω))iΛωε(ω))}  Equation (7)

Knowing the propagation function, the frequency-dependent open-circuitand short-circuit impedances are shown by Equations (8) and (9).Z _(open)(ω)=Z ₀(ω)cot h[γ(ω)l]  Equation (8)Z _(short)(ω)=Z ₀(ω)tan h[γ(ω)l]  Equation (9)

In the illustrative example, the length “l” of the insulated wire (i.e.,L_(T)) is 10 meters and yields the characteristic impedance Z₀(ω) shownbelow in Equation (10). $\begin{matrix}{{Z_{0}(\omega)} = \sqrt{\frac{{R(\omega)} + {{\mathbb{i}}\quad\omega\quad{L(\omega)}}}{{G(\omega)} + {{\mathbb{i}}\quad\omega\quad{C(\omega)}}}}} & {{Equation}\quad(10)}\end{matrix}$

The characteristic impedance can also be computed as the product of themeasured open-circuit and short-circuit impedances as shown below inEquation (11).Z ₀ ² Z _(short)(ω)Z _(open)(ω)  Equation (11)

Further, the propagation function can be found from the ratio of themeasured open-circuit and short-circuit impedances as shown in Equation(12). $\begin{matrix}{{{\gamma(\omega)}l} = {\tanh^{- 1}\sqrt{\frac{Z_{short}(\omega)}{Z_{open}(\omega)}}}} & {{Equation}\quad(12)}\end{matrix}$

Having obtained the characteristic impedance and the propagationfunction from the measured open-circuit and short-circuit impedance(i.e., using Equations (11) and (12)), the program can calculate thereal and imaginary components of the dielectric function. Equations (7),(10), (11) and (12) yield the following relationships shown in Equations(13) and (14). $\begin{matrix}{{{\gamma(\omega)}{Z_{0}(\omega)}} = {{R(\omega)} + {{\mathbb{i}}\quad\omega\quad{L(\omega)}}}} & {{Equation}\quad(13)} \\{\frac{\gamma(\omega)}{Z_{0}(\omega)} = {{\mathbb{i}}\quad\Lambda\quad\omega\quad{ɛ(\omega)}}} & {{Equation}\quad(14)}\end{matrix}$

Accordingly, the frequency-dependent resistance (R(ω)) per meter,inductance (L(ω)) per meter, real component of the dielectric function(ε(ω)), and imaginary component of the dielectric function (ε(ω)) can becalculated based on the characteristic impedance Z₀(ω) and propagationfunction γ(ω) as shown below in Equations (15), (16), (17) and (18).$\begin{matrix}{{R(\omega)} = {{Re}\left\lbrack {{\gamma(\omega)}{Z_{0}(\omega)}} \right\rbrack}} & {{Equation}\quad(15)} \\{{L(\omega)} = {{Im}\left\lbrack {{\gamma(\omega)}\quad{{Z_{0}(\omega)}/\omega}} \right\rbrack}} & {{Equation}\quad(16)} \\{{ɛ_{1}(\omega)} = {- {{Re}\left\lbrack \frac{\gamma(\omega)}{\omega\quad\Lambda\quad{Z_{0}(\omega)}} \right\rbrack}}} & {{Equation}\quad(17)} \\{{ɛ_{2}(\omega)} = {{Im}\left\lbrack \frac{\gamma(\omega)}{\omega\quad\Lambda\quad{Z_{0}(\omega)}} \right\rbrack}} & {{Equation}\quad(18)}\end{matrix}$

Therefore, having obtained the characteristic impedance and thepropagation function from the measured open-circuit and short-circuitimpedance (i.e., using Equations (11) and (12)), the program then usesEquations (17) and (18) to calculate the real (ε₁(ω)) and imaginary(ε₂(ω)) components of the dielectric function (ε(ω)). In theillustrative example, the structure factor (Λ) of the insulated wire iscalculated using the known illustrative diameter (d)=1 mm and knownillustrative center-to-center distance (s)=2 mm.

The real and imaginary components of the dielectric function for theimpedance data, as calculated by the program, are shown in FIGS. 10 and11, respectively.

Then, the program compares the calculated dielectric function to knowndielectric function values exhibiting various types of damage in a wire(step 904). The dielectric function of the wire exhibits two microscopicprocesses: a relatively slow ionic process (ε_(ionic)(ω)) that is on theorder of tens of milliseconds or longer, and a relatively fastelectronic process (ε_(e)(ω)) that is on the order of nanoseconds and isnearly independent of frequency. The dielectric function (ε(ω))including its components is shown in Equation (19), and the componentsε_(ionic)(ω) and ε_(e)(ω) are shown in Equations (20) and (21),respectively. $\begin{matrix}{{ɛ(\omega)} = {{ɛ_{ionic}(\omega)} + {ɛ_{e}(\omega)}}} & {{Equation}\quad(19)} \\{{ɛ_{ionic}(\omega)} = \frac{A_{s}ɛ_{0}}{1 + \left( {{\mathbb{i}}\quad\omega\quad\tau_{ionic}} \right)^{n_{ionic}}}} & {{Equation}\quad(20)} \\{{ɛ_{e}(\omega)} = \frac{B_{s}ɛ_{0}}{1 + \left( {{\mathbb{i}}\quad\omega\quad\tau_{e}} \right)^{n_{e}}}} & {{Equation}\quad(21)}\end{matrix}$

In Equations (19) and (20), ε₀ is the dielectric constant of vacuum,A_(s) is a geometric factor that is <<1, B_(s) is a geometric factorthat is ≈3-10, n_(ionic)≈1, n_(e)≦1, and τ is a time response. Thus, asthe ionic process is a slower process, the ionic process influences thelow frequency portion of the dielectric function's spectra, and thefaster electronic process influences a wider range of frequencies inthat it is larger than the ionic process.

A damage type database 228 contains frequency-dependent real andimaginary dielectric function data for combinations of known wire types,wire lengths, and damage types. The program compares the calculatedfrequency-dependant real and imaginary dielectric function values to thedamage type database entries to determine whether the wire is damaged.For each wire type, the damage type database containsfrequency-dependent real and imaginary dielectric function data for eachwire length and each damage type. For example, the damage type databasecan include entries for the wire types twisted-pair, coaxial, andparallel-conductor wire. The wire types can further be designated bytheir conductor and insulation materials. The wire lengths can bedelimited, for example, from 1 meter to 100 meters in 0.5 meterincrements. The types of damage can include exposure to hydraulic fluid,humidity, and mechanical wear. One having skill in the art willappreciate that damage type database can include alternative oradditional values. Further, the damage type database can be in a formother than a database, such as a multi-dimensional array.

A user of the data processing system can enter the wire type and wirelength as values, which are received by the program, to narrow thedatabase search to damage type database entries corresponding to therelevant wire type and wire length. If the calculatedfrequency-dependant real and imaginary dielectric function valuescorrespond to the values of one or more of the relevant dielectricfunction data in the damage type database, then the program determinesthere is damage along the wire of the relevant damage type.

As shown in step 906, the program then calculates thefrequency-dependent resistance of the wire. The frequency-dependentresistance of the wire can be affected by the skin effect, that is by anoxide layer or other type of layer contacting the conductor. In general,the resistance of the wire becomes frequency dependant when the skindepth in Equation (22) is satisfied. $\begin{matrix}{\omega \geq \frac{2}{\sigma\quad\mu\quad r_{0}^{2}}} & {{Equation}\quad(22)}\end{matrix}$In Equation (22), ω represents the frequency, σ represents conductivityof the conductor, μ is the magnetic permeability and is around 4π×10⁻⁷,and r₀ is the radius of the wire. Thus, the resistance increases withfrequency as ω^(1/2).

Using Equation (15), the program calculates the frequency-dependentresistance for the wire and compares the calculated values to knownvalues in the damage type database (step 908). Therefore, in addition tothe entries described above for each wire type, the damage type databasealso contains frequency-dependent resistance values. The programcompares the calculated frequency-dependent resistance to databaseentries for frequency-dependent resistance values corresponding to thesame or similar wire type and wire length. If the program determines thevalues match or substantially match, then the program determines thewire has damage of the relevant damage type.

Then, the program calculates the frequency-dependent inductance of thewire (step 910). The frequency-dependent inductance of the wire can alsobe affected by the skin effect. For example, the low frequencyinductance for a twisted pair wire is given by Equation (23).$\begin{matrix}{L = {\frac{\mu}{\pi}\quad{{Cosh}^{- 1}\left\lbrack \frac{s}{d} \right\rbrack}}} & {{Equation}\quad(23)}\end{matrix}$

In Equation (23), the magnetic permeability (μ) is about 4π×10⁻⁷. Forthe frequency range of around 100 kHz to around 1 MHz, the inductancedecreases gradually. This behavior is due to the inductance depending onthe magnetic field between the two conductors of the twisted-pair wire.When the skin effect is exhibited in one or both of the conductors ofthe twisted-pair wire, the inductance decreases more rapidly.

Using Equation (16), the program calculates the frequency-dependentinductance for the wire and compares the calculated values to knownvalues in the damage type database (step 912). Therefore, in addition tothe entries described above for each wire type, the damage type databasealso contains frequency-dependent inductance values. The programcompares the calculated frequency-dependent inductance to databaseentries for frequency-dependent inductance values corresponding to thesame or similar wire type and wire length. If the program determines thevalues match or substantially match, then the program determines thewire damage is of the relevant damage type.

Referring back to FIG. 4, if the program determines there is wire damagein step 406, then the program determines the amount of wire damage (step408). Through extensive experimentation, the inventors have discoveredthat the low-frequency portion of the phase of the measured broadbandimpedance spectrum of the wire is sensitive to damage along the wire. Ifthe wire is undamaged, the measured impedance phase spectrum isrelatively flat at around −90° over a range of low frequencies, such asfrom about 100 Hz to about 1 MHz. However, if the wire is damaged, thenthe measured impedance phase deviates from −90° in the low-frequencyrange, such as from about 1 kHz to about 100 kHz. Further, the greaterthe amount of damage, the greater the impedance phase generally deviatesfrom −90° to 0°.

FIG. 12 depicts illustrative frequency-dependent impedance phase spectrafor the wire for cases in which the wire has been damaged in variousamounts by exposure to hydraulic fluid. As shown, the wire damageimpresses its signature on the low-frequency portion (e.g., about 5 kHzto about 500 kHz) of the impedance phase spectrum. The greater theamount of damage, the greater the impedance phase generally deviatesfrom −90° to 0° at around 50 kHz. As shown, at 50 kHz, when there is nodamage (i.e., baseline) the impedance phase is around −90°, when thereis 0.5 meter of damage the impedance phase is around −89°, when there is1.0 meter of damage the impedance phase is around −88°, when there is1.5 meters of damage the impedance phase is around −87°, and when thereis 2.0 meters of damage the impedance phase is around −86°.

The frequency-dependent impedance phase spectrum for the wire in theillustrative example is thus depicted in FIG. 12 as the case in whichthere is 1.0 meter of wire damage. The program determines the amount ofwire damage by calculating the average impedance phase of the wire overa range of frequencies (e.g., about 0 Hz to about 1 MHz or higher) andcomparing the average impedance phase to values in a damage amount table224. Damage amount table 224 includes amount of damage values for knownwire types, wire lengths, types of damage, and average impedance phasevalues. As each of these variables impresses a signature on a wire, theamount of damage is determined by identifying a match corresponding tothe measured wire. In the illustrative example, damage amount table 224includes values for: wire types including twisted pair, coaxial, andparallel-conductor wires; wire lengths from 1 meter to 100 meters in 0.5meter increments; amounts of damage from 0 meters to 100 meters (limitedto the wire length) in 0.5 meter increments; and types of damageincluding exposure to hydraulic fluid, humidity, and mechanical wear.One having skill in the art will appreciate that damage amount table 224can include alternative or additional values. Further, damage amounttable 224 can be in the form of a data structure other than a table,such as a multi-dimensional array.

Knowing the wire type, the wire length and the type of damage, theprogram compares the calculated average impedance phase to the averageimpedance phase values of corresponding wire type, wire length, anddamage type entries in damage amount table 224. In the illustrativeexample, to determine the amount of damage, the program compares thecalculated average impedance phase of the measured impedance to theknown average impedance phase values for a 10 meter twisted-pair wirethat has been exposed to hydraulic fluid. Based on the known averageimpedance phase values in the damage amount table, the program woulddetermine that there is 1 meter of damage to the wire.

Alternatively, the program can analyze an impedance phase value otherthan the calculated average impedance phase value. For example, theprogram can analyze the measured impedance phase of the wire at aparticular frequency, such as 10 kHz, or determine whether the measuredimpedance phase has a value within a predetermined range (e.g., lessthan −90°) at a predetermined frequency (e.g., 10 kHz).

After determining the amount of wire damage in step 408, the programthen determines the location of the wire damage (step 410). Throughextensive experimentation, the inventors have discovered that thehigh-frequency portion of the phase of the measured broadband impedancespectrum of the wire is sensitive to the distance from the measurementpoint to the location of the damage along the wire. As the distance fromthe measurement point to the location of the damage to the wireincreases, the zero-crossing of the phase at high frequency shiftstoward a lower frequency.

FIG. 13 depicts illustrative frequency-dependent impedance phase spectrafor the wire for cases in which the wire has been damaged at variouslocations by exposure to hydraulic fluid. As shown, the illustrativewire damage impresses its signature on the high-frequency portion (e.g.,about 5.7 MHz to about 6.45 MHz) of the impedance phase spectrum, withthe phase spectrum for the case in which there is no damage (i.e.,baseline) having a zero crossing at about 6.45 MHz). The greater thedistance from the measurement point to the location of the damage, themore the zero-crossing of the phase spectrum deviates toward a lowerfrequency. The frequencies of the zero-crossings of the phase spectra ofFIG. 13 are summarized below in Table 1. TABLE 1 Distance frommeasurement Frequency of zero-crossing point to damage (m) (MHz) Nodamage ˜6.45 0-1 ˜6.40 1-2 ˜6.35 2-3 ˜6.30 3-4 ˜6.20 4-5 ˜6.10 5-6 ˜5.936-7 ˜5.90 7-8 ˜5.80 8-9 ˜5.75  9-10 ˜5.70

Referring to the illustrative example, the frequency-dependent impedancephase spectrum for the illustrative wire is thus depicted in FIG. 13 asthe case in which the damage is located 5-6 meters from the measurementpoint. The program determines the location of the wire damage bycomparing the zero-crossing of the phase of the measured impedance toknown zero-crossings of phases over a range of frequencies (e.g., about1 MHz to about 100 MHz or higher) that are stored in a data structure,such as a zero-crossing table 226. Zero-crossing table 226 includeszero-crossing values for known wire types, wire lengths, types ofdamage, and distances from measurement points to damage locations. Aseach of these variables impresses a signature on a wire, the location ofdamage is determined by identifying a match corresponding to themeasured wire. In the illustrative example, zero-crossing table 226includes values for: wire types including twisted pair, coaxial, andparallel-conductor wires; wire lengths from 1 meter to 100 meters in 0.5meter increments; types of damage including exposure to hydraulic fluid,humidity, and mechanical wear; and distances from the measurement pointto the damage from 0 meters to 100 meters (limited to the wire length)in 1.0 meter increments. One having skill in the art will appreciatethat zero-crossing table 226 can include alternative or additionalvalues. Further, zero-crossing table 226 can be in the form of a datastructure other than a table, such as a multi-dimensional array.

Knowing the wire type, the wire length and the type of damage, theprogram compares the measured high-frequency impedance phasezero-crossing to the zero-crossing values corresponding to the same orsimilar wire type, wire length, and damage type entries in zero-crossingtable 226. In the illustrative example, to determine the location of thedamage, the program compares the measured impedance phase zero-crossingto the known zero-crossing values for a 10 meter twisted-pair wire thathas been exposed to hydraulic fluid. Based on the known zero-crossingvalues in the zero-crossing table, the program would determine that thedamage is located from 5-6 meters from the measurement point.

If the program determines in step 406 that there is no wire damage orafter the program locates the wire damage in step 410, then the programdisplays the results of the analysis, for example, on the display device(step 412). The results include, for example, the type of damage, theamount of damage, and the location of the damage. In the illustrativeexample, the program displays that, at 5-6 meters from the measurementpoint, a 1 meter segment of the wire has been damaged by exposure tohydraulic fluid. Alternatively, the program can display additional oralternative results.

Therefore, methods, systems, and articles of manufacture consistent withthe present invention determine the type of damage to a wire, the amountof damage, and/or the location of the damage from a single measurementpoint on the wire. Further, the methods, systems, and articles ofmanufacture consistent with the present invention provide beneficialimprovements over conventional approaches, in that: wire prognosis canbe performed; impedance is measured from a single measurement point;and/or as the impedance is measured from a single measurement point,there is a reduced risk of damaging the wire.

The foregoing description of an implementation of the invention has beenpresented for purposes of illustration and description. It is notexhaustive and does not limit the invention to the precise formdisclosed. Modifications and variations are possible in light of theabove teachings or may be acquired from practicing the invention. Forexample, the described implementation includes software but the presentimplementation may be implemented as a combination of hardware andsoftware or hardware alone. Further, the illustrative processing stepsperformed by the program can be executed in an different order thandescribed above, and additional processing steps can be incorporated.For example, the program can locate the wire damage prior to determiningthe amount of damage, and the program can calculate the inductance ofthe wire prior to calculating the wire's resistance. The invention maybe implemented with both object-oriented and non-object-orientedprogramming systems. The scope of the invention is defined by the claimsand their equivalents.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1. A method in a data processing system having a program for identifyingdamage to a wire, the method comprising the steps of: obtaining abroadband impedance information for the wire from a single measurementpoint; determining a type of damage to the wire based on the broadbandimpedance information; and determining a location of damage along thewire by comparing a high-frequency phase information of the obtainedbroadband impedance information to at least one known high-frequencyphase information corresponding to a known location of damage.
 2. Amethod of claim 1 wherein the broadband impedance information isobtained from a single measurement point on the wire.
 3. A method ofclaim 1 wherein the step of determining the type of damage comprises:calculating a frequency-dependent dielectric function of the wire basedon the obtained broadband impedance information; and comparing thecalculated frequency-dependent dielectric function to at least one knownfrequency-dependent dielectric function corresponding to a known type ofdamage.
 4. A method of claim 1 wherein the step of determining the typeof damage comprises: calculating a frequency-dependent resistance of thewire based on the obtained broadband impedance information; andcomparing the calculated frequency-dependent resistance to at least oneknown frequency-dependent resistance corresponding to a known type ofdamage.
 5. A method of claim 1 wherein the step of determining the typeof damage comprises: calculating a frequency-dependent inductance of thewire based on the obtained broadband impedance information; andcomparing the calculated frequency-dependent inductance to at least oneknown frequency-dependent inductance corresponding to a known type ofdamage.
 6. A method of claim 1 further comprising the step ofdetermining an amount of damage to the wire by comparing a low-frequencyphase information of the obtained broadband impedance information to atleast one known low-frequency phase information corresponding to a knownamount of damage.
 7. (canceled)
 8. A computer-readable medium containinginstructions that cause a data processing system having a program toperform a method for identifying damage to a wire, the method comprisingthe steps of: obtaining a broadband impedance information for the wirefrom a single measurement point; determining a type of damage to thewire based on the broadband impedance information; and determining alocation of damage along the wire by comparing a high-frequency phaseinformation of the obtained broadband impedance information to at leastone known high-frequency phase information corresponding to a knownlocation of damage.
 9. A computer-readable medium of claim 8 wherein thebroadband impedance information is obtained from a single measurementpoint on the wire.
 10. A computer-readable medium of claim 8 wherein thestep of determining the type of damage comprises: calculating afrequency-dependent dielectric function of the wire based on theobtained broadband impedance information; and comparing the calculatedfrequency-dependent dielectric function to at least one knownfrequency-dependent dielectric function corresponding to a known type ofdamage.
 11. A computer-readable medium of claim 8 wherein the step ofdetermining the type of damage comprises: calculating afrequency-dependent resistance of the wire based on the obtainedbroadband impedance information; and comparing the calculatedfrequency-dependent resistance to at least one known frequency-dependentresistance corresponding to a known type of damage.
 12. Acomputer-readable medium of claim 8 wherein the step of determining thetype of damage comprises: calculating a frequency-dependent inductanceof the wire based on the obtained broadband impedance information; andcomparing the calculated frequency-dependent inductance to at least oneknown frequency-dependent inductance corresponding to a known type ofdamage.
 13. A computer-readable medium of claim 8 further comprising thestep of determining an amount of damage to the wire by comparing alow-frequency phase information of the obtained broadband impedanceinformation to at least one known low-frequency phase informationcorresponding to a known amount of damage.
 14. (canceled)
 15. A dataprocessing system for identifying damage to a wire, the data processingsystem comprising: a memory having a program that obtains a broadbandimpedance information for the wire from a single measurement point,determines a type of damage to the wire based on the broadband impedanceinformation, and determines a location of damage along the wire bycomparing a high-frequency phase information of the obtained broadbandimpedance information to at least one known high-frequency phaseinformation corresponding to a known location of damage; and aprocessing unit that runs the program.
 16. A data processing system ofclaim 15 wherein the broadband impedance information is obtained from asingle measurement point on the wire.
 17. A data processing system ofclaim 15 wherein the program determines an amount of damage to the wireby comparing a low-frequency phase information of the obtained broadbandimpedance information to at least one known low-frequency phaseinformation corresponding to a known amount of damage.
 18. (canceled)19. A wire analyzer for identifying damage to a wire, the wire analyzercomprising: means for obtaining a broadband impedance information forthe wire from a single measurement point; means for determining a typeof damage to the wire based on the broadband impedance information; andmeans for determining a location of damage along the wire by comparing ahigh-frequency phase information of the obtained broadband impedanceinformation to at least one known high-frequency phase informationcorresponding to a known location of damage.